Vertically Aligned Carbon Nanotubes as Platform for Biomimetically Inspired Mechanical Sensing, Bioactive Surfaces, and Electrical Cell Interfacing

Abstract

Vertically aligned carbon nanotubes (VACNTs) are one dimensional carbon objects anchored atop of a solid substrate. They are geometrically fixed in contrast to their counterparts, randomly oriented carbon nanotubes (CNTs). In this progress report, the breadth in which these one dimensional, mechanically flexible, though robust and electrical conducting carbon nanostructures can be employed as functional material is shown and our research is put in perspective to work in the last five to ten years. The connection between the different areas touched in this report is the biomimetic‐materials approach, which rely on the hairy morphology of VACNTs. These properties in connection with their electrical conductivity offer possibilities towards new functional features and applications of VACNTs. To appreciate the possibilities of biomimetic research with VACNTs, first their material characteristics are given to make the reader familiar with specific features of their synthesis, the peculiarities in arranging and controlling the morphology of CNTs in a vertical alignment as well as a current understanding of these properties on a microscopic basis. In doing so, similarities as well as differences, which offer new possibilities for biomimetic studies of VACNTS with respect to multiwalled randomly oriented CNTs, will become clear.

Effect of Hydrogen Concentration on the Growth of Carbon Nanotube Arrays for Gecko-Inspired Adhesive Applications

“…The morphology and quality of the resulting CNTs depend on the catalyst, carbon source, temperature, flow rate, and feedstock pressure during CVD, among other factors [30]. Schneider [31] considered that the CVD growth process of VACNTs could be a complex situation, in which all of the parameters have to be precisely-tuned, individually against each other (such as processing parameters, size of the reactor, dwell time and sample positioning in the reactor) to obtain a CNT material with certain structure in the most reproducible way. During CVD, the mixture gas typically includes a carbon source, a reducing gas, and an inert carrier gas, which is then fed into an airtight tube furnace.…”

“…It is generally accepted that the type and flow rate of the carbon source will affect the number of carbon atoms provided for CNT formation, and the accumulation of impurities (such as amorphous carbon) due to the self-decomposition of the carbon source is one of the reasons for the termination of CNT growth [35]. Studies regarding the influence of the reducing gas (usually hydrogen) in growth kinetics are relatively rare, although its effect on nanotube morphology has been investigated extensively [31,36]. One widely accepted theory is that hydrogen can remove the barriers for CNT growth by etching the impurities on the catalyst surface [37][38][39].…”

Bioinspired Fluffy Fabric with In Situ Grown Carbon Nanotubes for Ultrasensitive Wearable Airflow Sensor

“…Upon the application of airflow, the number of contact points between the extended CNTs significantly increase induced by the bending of the CNTs, [35,36] for which the corresponding resistance is defined as the bending contact resistance (R Bend ). Meanwhile, the curved foam-like CNTs experience strong compressions [37][38][39][40][41] induced by the airflow, also leading to a rise in the number of contact points. The corresponding resistance is defined as the compression contact resistance (R Comp ) (Discussion S1, Supporting Information).…”

Human Eye Optics within a Non-Euclidian Geometrical Approach and Some Implications in Vision Prosthetics Design

“…Neuronal photoactivation is possible using QDs in conjugation with vertically aligned carbon nanotubes (VACNTs), representing a cutting-edge technological solution. VACNTs have excellent electrochemical, biocompatible and durability properties [78], making them excellent candidates for ultradense microelectrode arrays (diameter 20-200 µm) [79,80]. VACNT-based electrodes deliver these stimulating pulses to the central nervous system optical fibers, initially targeting the surviving bipolar cells which transfer the signal through the ganglion cell layer.…”